Construction employers have backed Victorian government moves to ensure all workers on government projects face random drug and alcohol testing from July 1.

But the Construction Forestry Mining and Energy Union (CFMEU) has dismissed the need for testing as a stunt ahead of the November state election.

Victorian Finance Minister Robert Clark says that from July 1, all building companies that tender for taxpayer-funded projects worth $10 million or more must test workers for drugs and alcohol use.

Head contractors must perform a minimum number of random tests on workers each month and identify what methods they would use, Mr Clark said on Friday.

Contractors would determine the level of intoxication they deem unsafe and how workers would be sanctioned if drugs or alcohol were detected in their systems, he said.

Tenderers will have to list site security measures, which may include CCTV, a swipe card access system and photographic or biometric security systems in a bid to stamp out criminal activity.

Mr Clark said the measures would cut intoxication, drug dealing, fraud and theft at building sites.

"We are introducing these guidelines to ensure that every contractor that tenders for Victorian government construction projects need to commit to have processes in place to guard against drug and alcohol abuse in their workplaces and also to ensure site security," he said.

"Every construction worker has the right to feel safe from the risks posed by anyone affected by drugs and alcohol on a risky construction site. Those who are doing the right thing will have nothing to fear," he said.

But CFMEU Victorian secretary John Setka said there was no evidence of widespread intoxication, drug problems, theft or fraud on Victorian building sites, nor that random testing would improve health and safety.

"If the government has any evidence of these claims they should produce them in parliament for the benefit of the people of Victoria," he said.

"This is a hysterical appeal to voters without any consideration for factual accuracy."